UMass researchers look at culverts’ effects on wildlife

AMHERST — Culverts and bridges are meant to help cross streams and small waterways, but a 2-year-long review of culverts, bridges and dams all across Massachusetts has found that many cause major problems for fish and other aquatic wildlife.

University of Massachusetts researchers who analyzed thousands of road-stream crossings found that outdated or poorly designed culverts and other structures can impede the normal movement of such wildlife as brook trout and migrating alewife. The same structures can also pose dangers for humans by increasing the risk of flooding or by forcing larger animals like bobcats or black bears onto roadways where they might collide with motorists.

Researchers working on the study funded with $585,000 from the Massachusetts of Transportation and the Nature Conservancy, improvements to just 10 percent of the crossings would have a significant positive impact on wildlife.

Roads, bridges, culverts and dams “sometimes … create barriers that harm migrating fish and other wildlife that require connected habitat to survive. “The fragmentation of this habitat is one of the major challenges faced by Massachusetts wildlife,” said Scott D. Jackson, extension associate professor of environmental conservation.”

The “Critical Linkages” project provides easily accessible data that can help identify specific locations where changes to important infrastructure—bridges, culverts, roads and dams—would be most effective in providing benefits for wildlife and the habitat on which they rely.

Researchers analyzed 48,859 miles of roads and highways, 26,582 road-stream crossings such as culverts and bridges and 2,467 dams in areas including the Deerfield, Westfield and Housatonic watersheds, in combination with sophisticated information about wildlife habitat to identify places where changes would have the greatest impact.

“We suspect that the structures that are the biggest barriers for fish and wildlife are also the ones most vulnerable to being washed out,” Jackson said. “In the last couple of years, we’ve started to think more about how our data collection in the field and how our analysis might actually serve double duty to identify those road stream crossings that are at most risk of failure. That’s something that’s in the works.”

The transportation department has already used the information to set priorities for several projects, including replacing an undersized Route 2 culvert over Hartwell Brook in Charlemont.

The U.S. Forest Service has done analysis that have shown that the structures that era the biggest barriers to fish are also the ones that tend to be undersized and most likely to be overwhelmed in a storm, Jackson said.

“There’s a sense that if you design crossings in a way that allows good passage, at the same time, you’re going to create structures that are fairly resilient in the face of not only the current storms that we get now, but the kind of more sever storms that we think we’re going to get if climate change continues to kick in.”

As more crossings are assessed by researchers who visit them in the field, researchers will continue to apply the models to results in those watersheds.

Maps and data from the recently concluded first phase of the project can be found at www.umasscaps.org